1. Field of Invention
The present invention relates to a method for determining model parameters of a Silicon On Insulator (SOI) Metal Oxide Semiconductor Field Effect Transistor (MOSFET) device, and particularly to a method for determining BSIMSOI4 Direct Current (DC) model parameters, belonging to the field of micro-electronic device modeling.
2. Description of Related Arts
An MOSFET is a four-port semiconductor device, where different excitation is applied to each port, and a drain current of the device also changes accordingly. An input/output mathematical expression is obtained by establishing a mathematical model of the device, and circuit designers use the model to perform SPICE emulation of circuit design. Currently, multiple kinds of mathematical models with respect to the MOSFET are proposed, and each kind of model includes a large number of parameters. A BSIM model is a standard of a device model, and is widely used by semiconductor manufacturers.
Due to a complicated physical mechanism in the SOI MOSFET device, the SOI MOSFET device has a more complicated model equation and more model parameters than a bulk silicon device. For a device of a floating structure, since a body area is not connected to the outside and is in an electrical “floating” state, when the device actually works, various current components (a junction current, a parasitic triode current, a gate-to-body current, and a gate-induced drain leakage current) flowing into the body area results in charge accumulation and a non-constant potential in the body area, further causing a Kink effect and a GIFBE effect. In addition, since a bottom portion of the SOI MOSFET device has a layer of low-thermal conductivity Buried Oxide (BOX) layer, during a DC test, there is no time to reduce the temperature, enabling the channel temperature to be higher than the environment temperature, that is, a “self-heating effect” occurs. However, in an actual digital circuit application, the device works in a rapid turn-on/off state, there is no time to accumulate heat, so the “self-heating effect” is not obvious or disappears.
An accurate device model is a reliable guarantee of circuit emulation. Only after all parameters related to the body area and the self-heating effect are accurately extracted, a success rate of Integrated Circuit (IC) design based on an SOI process can be improved. A BSIMSOI4 model system includes abundant model equations of a junction current, a parasitic triode, and the like, and can effectively describe the foregoing effects. BSIMSOI4 has tens of parameters for describing unique SOI properties. Special test conditions need to be set, so as to obtain accurate parameters. Compared with other solutions, the present invention provides a more accurate and more effective method for extracting BSIMSOI4 model DC parameters.